Process for desulfurizing and reforming hydrocarbons



April 15, 1947. l

s. G. oBERFELL PROCESS FOR DESULFURIZING AND REFORMING HYDROCARBONS- Fild April 11, 1941 y g l l y "1 HBMOL .LSA-mvo BLENDING }7/' TANK INVENTOR GEORGE G. OBERF ELL Patented pr. 151? 194i PROCESS FOR DESULFURIZING ANDA REFORMING HYDROCARBONS George G. Gberfell, Bartlesville, Okla., assignor` to Phillips Petroleum Company, a corporation of Delaware Application April 11, 1941, Serial No. 388,153 s claims. (o1. 19a-'24) This invention relates to the treatment of hydrocarbon oils and is directed more particularly to the treatment of lighter fractions of petroleum oils such as those producedby cracking of heavier petroleum oils, by straight run distillation of such oils or by extraction of liquid fractions from natural gas, as Well as lighter hydrocarbon fractions obtained from shales, destructive hydrogenation of coal, and the like. The term distillate When used in this'specification does not indicate any limitation as to the source of the material described.

More specifically, the present invention contemplates the treatment of relatively low boiling vhydrocarbon fractionsfor the kproduction of an improved motor fuel and for the removal of sulfurtherefrombyanovel and emcient method hereinafter described. This method offers distinct advantages over other methods at presentemployed in that it is specifically directed toward the removal of all types of sulfur compounds, including those which are especially refractory or resistant to the action of the reagents and proc esses known to the prior art. f This invention contemplates further the production of an improved motor fuel having an increased octane number and tetraethyl lead'susceptibility by blending the products of desulfurization and dehydrogenation treatments carried out in a manner hereinafter more fully described.

It has become general practice to improve the anti-knock value of motor fuels by adding lead alkyls thereto in small quantities. However, it has been found that motor fuels vary greatly vin their response to this treatment. For example, of two motor fuels with equal anti-knock value before addition of tetraethyl lead, one may show an increase often octane numbers and the other only five, followlng'additionfof one cubic centimeter of tetraethyl lead per gallon of motor fuel. The increase inoctane number obtained by adding a given quantity of tetraethyll lead to a gallon of 'motor fuel has'been termed the lead vre-A sponse or lead susceptibility of the fuel.

, The present invention is partially basedupon the discovery that differences in lead response v among motor fuels, of substantially the same hydrocarbon composition are duev to certainV impurities present in most-motor fuelswhich greatly reduce the effectiveness of tetraethyl lead in suppressing knocking in internal combustion engines. These impurities areA of the sulfur, nitrogen and oxygen type, of which the sulfur compounds appear to be the most important. Thus, removal of these impurities and particularly the sulfur compounds results in an improved lead response.

In ordinary refining practice, the methods and reagents heretofore in use are effective for the removal of some of the types of vsulfur compounds present in petroleum distillates. For example, elementary sulfur, mercaptans, sulfldes and disulfides are relatively easily removed, While the heterocyclic sulfur compounds such as the thiophenes and thiophanes are quite refractory and difficult to remove by simple methods. The most difficult types of distillates todesulfurize are th'ose which result from cracking of higher boiling hydrocarbons, especially those Which contain a relatively high percentage of sulfur, thus resulting in the formation of distillates containing sulfur predominantly in the form of refractory heterocyclic or other compounds. Such distillates require severe treatment for the removal of the refractory sulfur compounds. y

fk It is, therefore, one of the objectsof this "in-v vention to improve the lead response of motor fuels by an improved method of reducing the sulfur content of such fuels.

It is another object of the present invention to provide a sequence of steps which will effectively remove refractory sulfur compounds from hydrocarbons containing the same, such as cracked distillates, and which will enable the production of a motor fuel having improved leadresponse and anti-knock characteristics.

It is a further object of this invention to treat different hydrocarbon .materials so as to ,enable the production of` animprovedmotor fuel blend of increased octane numberand lead susceptibilf: l

ity in an economical manner. l Improved motorfuels maybe produced in acv cordancewith my invention by subjecting natural carrying' out the other, and blending the resultingv Accordingly,y the` products' ofV each treatment.

natural and/or straight run gasoline is subjected to a combined desulfurization-reforming operation, preferably under mild conditions of temperature with the aid of certain catalysts. In this treatment a certain amount of dehydrogenation occurs and hydrogen is produced and recovered therefrom and utilized in another portion of the process. In this step of the process, the gasoline treated is improved by effecting changes in hydrocarbon structure such as isomerization, lowering of the sulfur content and the production of certain unsaturated hydrocarbons which are known to affect favorably the antiknock properties of the resultant fuel.

The second portion of my process includes a hydrogenation step and is applied to fuels comprising cracked distillates which contain the more refractory sulfur compounds referred to above. This hydrogenation may be either simple or destructive and with or without known hydrogenation catalysts and accomplishes desulfurization to a degree which depends upon the hydrogenation conditions. A further effect of 'this hydrogenation is that the distillate is stabilized against subsequent gum and color formation by the action of hydrogen on the sulfur compounds and on the highly unsaturated compounds which are found in cracked materials, especially conjugated diolens, which tend to polymerize and oxidize very readily. The completeness of stabilization depends, of course, on the type of material treated and the hydrogenation conditions. Usually no further treatment for removing gum-forming substances is necessary, although sometimes a slight clay or other treatment is found advisable. The sulfur and highly unsaturated compounds are hydrogenated without a great deal of concomitant hydrogenation of mono-olens to parafns, which latter reaction of course would be undesirable and cause loss in octane number of the cracked stock.

The hydrogen produced in the reforming or dehydrogenation operation as described in connection With the first portion of my process is of considerable quantity, and may be as much as 50-90% of the off gases. This hydrogen may be readily separated from other constituents of the off gases such. as methane and hydrogensulde, and then be utilized in the hydrogenation step in the second portionof the process. The hydrogen may be recycled in the hydrogenation step.

The products of the aforesaid reforming and hydrogenation operations may then be blended as desired to produce an improved motor fuel.

As referred to above, cracked distillates contain certain refractory sulfur compounds which are not completely removed by a single hydrogenation step as described above. Accordingly, as a modification of the above described method, I have found that the aforesaid refractory sulfur compounds can be removed in a simple, economical and effective manner by subjectingV the hydrocarbons to be treated to a two-step treatment in place of the single hydrogenation step in the second portion of my process. In the rst step the hydrocarbon iscontacted in vapor form with hydrogen at elevated temperatures in a relatively high ,pressure zone of say, 500-to 1,000 pounds pressure, orv even more. The conditions of temperature, pressureand reaction time are selected so as to avoid appreciable thermalv decomposition or cracking of the.- hydrocarbons, and since no catalyst is present in this step, it is one in Awhich purely thermal hydrogenation takes place. In

the place of the aforesaid thermal treatment a mild catalytic hydrogenation step may be used under conditions Which avoid cracking or decomposition of the hydrocarbons.

The effluent from this rst step is then passed to the second step which is a. low pressure catalytic desulfurization or a reforming operation, depending on the type of material initially treated and upon the nature of the desired product. This second operation may conveniently be that which is utilized in the first portion of my process for the treatment of natural and/or straight run gasolines, the second step in the treatment of cracked distillates being thereby combined with the rst portion of the process, a -blending of the fuels being obtained thereby and the dehydrogenation or reforming step having a dual function. The hydrogen produced in this step is conveniently and economically utilized in the hydrogenation operation as heretofore explained.

Referring to the drawing wherein there is diagrammatically illustrated one form of apparatus for carrying out my invention and its modications, the low octane material such as straight run or natural gasoline is introduced through pipe 9, and preheating furnace Iil into reaction zone I I at the proper temperature and pressure for reforming. The reaction zone II contains a catalyst, preferably bauxite, which is capable of bringing about desulfurization and reforming With iscmerization and concomitant dehydrogenation. The said zone is maintained at a suitable reforming temperature, in the,V case of bauxite within the range of o-1200" andat pressures of atmospheric or higher Ibut generally below y pounds per square inch. Flow rates are so chosen that only a minimum of cracking occurs. The effluents from the reforming zone H pass through pipe AI2 to condenser I3 wherein the improved motor fuel` is condensed and then to separator Ill wherein the condensate is separated from the gaseous eiiluent of the reforming operation and may be withdrawn from the system through line I5` containing valve I6 to blending tank I'I. A compressor is indicated at I8 which may be utilizedv if desired ,to aid in the condensation. Y

The gaseous fraction from the separator I4 will contain from about fty to ninety per cent hydrogen, depending upon the reforming conditions. the remainder beinelareely hydrogen su1- deand methane with Smaller amountsv of yother rlQrmifJlyy gaseous hydrocarbons. This fraction is passed through line IS, and compressor 2,0 to separator 2l whereinv hydrogen 0f sucient purity for use in hydrogenation operations is separated from the other constituents ofthe gaseous fraction, This separation may take the form' of chemical or catalytic removal of; hydrogen sulde, fractionation, o r oil absorptionifdepending upon the economics of the installationu andthe compositionof the hydrogen-bearing gas. The undesired gases are Withdrawn. from; the system through oneV or, more valved lines, represented in the drawing by line. 2:2` containing valve 23, 'and they purified hydrogen is passed through line 24 to heater 25, and toihydrogenatorez. f

. If desired; a portion of hydrogen may be recycled to reactionizone I'I by passingit through line 2l.,controlledby valve 2B into heater III, where it is `rnixedwith the incoming charge stockin pipes. This recycling of hydrogen gives very desirable results. Presumably it may depress the dehydrogenation reaction somewhatbut sucient additional isomerization.. apparently takes place under these conditions to more than make up for the lowered content of unsaturated material, so that an increased octane number is obtained.

Unsaturated hydrocarbons, such as cracked gasoline, or the like are introduced into the system through line 29 where they pass through line 24, in admixture with hydrogen from the separator, and through furnace 25 to the hydrogenator 26. A compressor 30 in line 24 may be used if necessary. The mixture of hydrogen and unsaturated hydrocarbons is maintained under known conditions of temperature, pressure and reaction time' suitable for hydrogenation. The hydrogenation operation may be either thermal or catalytic, and either simple or destructive, depending upon the stock t be hydrogenated and the result desired, as will be well understood by those skilled in the art in the light of the present disclosure. The effluents from hydrogenator 2B pass through line 3I containing valve 32 to condenser 33 and then to separator 34, wherein the hydrogenated products liquefied in condenser 33 are separated and withdrawn from the system through line 35 containing valve 35 to blending tank I1. Of course, the operation of separator 34 will vary with the type of material treated and the type of hydrogenation carried out, in order to obtain a product of motor fuel boiling through line 3I, controlled by valve 38, and line I9 to separator 2| wherein the hydrogen is again puried and then recycled. Line 39 controlled by valve 40 provides for withdrawal of suitable quantities of hydrogen and 'any other gases separated in separator 34 in the event that more hydrogen is produced than consumed, thus tending to pyramid in the system.

Line 4I containing valve 42 and line 43 containing valve 44 branch olf from lines I5 and 35 respectively to allow the withdrawal of products in case there is an excess of one or the other over that required for blending in tank I1, blending of products in tank I'I produces an improvedmotor fuel having the desirable properties referred to above.

This process is especially economical in the use of heat, and in the operation of the process a The ' takes place.

6 formingl step II.` The thermal'operation may be carried out at a pressure of 500 to 1,000 pounds and at a temperature ofabout 550 to '750 F. A mild catalytic step may be used in place of the thermal hydrogenation, using a mild hydrogenation catalyst such as molybdic oxide-nickelous oxide at temperatures below cracking or decomposition, In using the modified method vonly for treating cracked distillates for the removal of refractory sulfur compounds therefrom, no straight run distillate is introduced into the apparatus at 9 and the desulfurizing and reforming operation at I I becomes the second'step in the process receiving the pre-treated cracked distillate from the hydrogenating' operation 26. In this case, it is usually preferred to maintain the desulfurizing catalyst in tower II-at a somewhat lower temperature than when natural gasoline or straight run distillate is concomitantly reformed.

Another useful modification is to maintain a temperature gradientor two temperature zones in catalyst tower VI I, and to introduce the cracked distillate which has already been treated with hydrogen through line 45 and valve 50, valve 49 being closed into the 10W-temperature zone 5I of the catalyst, wherein further desulfurization The cracked stock may be blended with straight run or natural stock either before or after it has passed through the low-temperature zone, and either before or after said straight run or natural stock has been desulfurized and reformed in the high-temperature zone. Using bauxite, for example, as a catalyst, the hightemperature zone would be held at from about 900 to 1200" F. while the low-temperature zone would be maintained at from about 500 to 800 F.

I claim:

1. A process for producing an improved motor fuel which comprises contacting a rst motor fuel of relatively low antiknock value and lead susceptibility and containing sulfur in substantially non-refractory form with a reforming catalyst in a reforming step under conditions of temperature, pressure and rate of ow such that substantially no cracking takes place but hydrogen is produced and desulfurization occurs, contacting a second motor fuel consisting of a cracked distillate containing refractory sulfur compounds number of heat-exchanging steps are utilized which are not shown in the drawing, being obvious to those skilled in the art.

A modification of the process as hereinabove described is illustrated by line 45 controlled by valve 4B, which conducts the hydrogen-treated cracked distillate through furnace 41, line 48 and valve 49, valve 50 being closed to the low pressure catalytic desulfurizing or reforming zone II. 'Ihere the refractory sulfur compounds which have been initially treated in the preliminary hydrogenation step 26 are finally converted to hydrogen sulfide, and thus removed. Also, the cracked distillate may be blended in catalyst tower II with the straight run material which may be introduced into the system through pipe 9. When this modification of the invention is used, it is desirable that the hydrogenation step 26 be one which is either thermal or a mild in the low pressure catalytic desulfurizing or reand unsaturates, with hydrogen at elevated tem.. peratures and pressures but below reforming temperatures in a separate step to effect hydrogenation and pre-treatment of said refractory sulfur compounds, introducing said hydrogenated and pre-treated cracked distillate into the reforming step to eliminate said sulfur compounds, whereby said cracked distillate and said first motor fuel are blended, and withdrawing the blended motor fuel obtained thereby.

2. A process according to claim 1 in which the reforming step comprises at least two zones, one of which is maintained at a lower temperature than the other, vand in which the pre-treated cracked distillate is introduced into the lower temperature zone.

3. A process for producing an improved motor fuel which comprises contacting a first motor fuel of relatively low antiknock value and lead susceptibility and containing sulfur in substantially non-refractory form with a reforming catalyst in a reforming step at a temperature of about 900 to l200 F., and a pressure and rate of flow such that substantially no cracking takes place buthydrogen is produced and desulfurization occurs, contacting a second motor fuel consisting of a cracked distillate containing refractory sulfur compounds and unsaturates with hydrogen at a temperature of about 550 to 750 F., and a pressure of about 500 to 1000 pounds in a separate step to eiect hydrogenation and pre-treatment of said refractory sulfur compounds, introducing said hydrogenated and pre-treated cracked distillate into the reforming step to eliminatesaid sulfur compounds, whereby said cracked distillate and said rst motor fuel are blended, and withdrawingl the blended motor fuel obtained thereby. GEORGE G. OBERFELL.

REFERENCES CITED The following references are of record 1n the le of this patent:

UNITED STATES PATENTS Number Name l l Date` v 1,152,765 Sabatier et al Sept. 7, 1915 2,143,472 Boultbee Jan, 10, 1939 2,160,136" Frolich May 30, 1939 2,167,602 Schulze July 25, 1939 Number Name Date 2,202,401 Rosen f .1 1 -1 May 28, 1940 2,242,504 Benedict et al. May 20, 1941 2,249,595 Benedict July 15, 1941 2,273,293 Szayna f Feb. 17, 1942 2,289,716 .Mars'c-hner July 14, 1942 2,293,759 Penisten Aug. 25, 1942 2,291,885 Egli Aug. 4, 1942 2,037,792 Ipatei ;1 A Apr. 21, 1936 2,042,298 Davis May 26, 1936 2,143,078 Lyman et al 1., Jan, 10, 1929 2,298,347 COISOI et al. Ot. 13, 1942 FOREIGN PATENTS Number Country Date 427,905 British v l r l May V2, 1935 749,843 French 1 May 15, 1933 OTHER REFERENCES Hydrogenation of Petroleum, R. T. Haslam and. R. P, Russell, Industrial and Engineering Chemistry, Oct. 1930, pages 1030-1037,. (Copy in Library.) 

